The Rufiji Estuary: Climate Change, Anthropogenic Pressures, Vulnerability Assessment and Adaptive Management Strategies

Abstract

The Rufiji Estuary supports the largest mangrove area (48,030 ha) in Tanzania, which, together with nearby seagrass beds, numerous coral reefs and islands, form an interacting seascape that provides invaluable ecological services to the Western Indian Ocean. For centuries, the Rufiji resources have been utilized sustainably by coastal people for food, firewood and building materials. However, in recent decades, the Estuary has been severely affected by a complexity of both climate change factors and anthropogenic pressures. A WWF/GEF Coastal Resilience to Climate Change Project was conducted between 2007 and 2009, involving repeated quantitative ecological plot assessment, rapid assessment, remote sensing (based on satellite images taken in 1991 and 2000) and recording indigenous knowledge through social science methods. Change analysis showed several definite trends. Along exposed seaward edges (not sheltered by reefs or islands), there was drastic erosion and mangrove loss attributed to increased wave activity and sea level rise, with over 25 m of coastline being lost along sections of the estuary over a two-year period. Along other seaward edges, some accretion and mangrove growth occurred due to being sheltered from wave action and having adequate sediment load from Bumba channel, which has received the main flow of Rufiji since the shift of the river in 1978. The 1998 El-Nino flooding event caused drastic mangrove loss in riverine areas. On several landward edges of the delta, migration of mangroves inland was detected. Overall, however, losses of mangroves in the Rufiji were clearly greater than gains. Anthropogenic pressures include deforestation in the watershed area and large scale cutting of mangroves for timber and conversion to rice farms. Recommended mitigation and adaptive management strategies include the establishment of buffer zones, mangrove planting, awareness raising and enforcement.